Linear motion bearings have been known in the art and, for example, have been shown in the U.S. Pat. No. 2,628,135. Bearings such as this require accurate mounting to achieve their maximum usefulness, and if they are made in multiples, that is multiple pillow blocks are placed end-to-end to provide a long bearing unit, it is obvious that very tight tolerance will have to be maintained to prevent the bearings within the adjacent pillow blocks from crabbing, that is assuming an angular relationship one to the other. This is even true when the so-called self-aligning bearings are used as, for example, the type shown in U.S. Pat. No. 3,588,200. It becomes apparent that pillow blocks require extreme parallelism of the mounting surfaces to avoid damage to their bearings, and when it is necessary to use bearings in tandem to increase the load capacity, alignment is time consuming and it is of course time consuming to bore aligned holes in the bearing housings to maintain the necessary accuracy.